On 09/11/2011 09:27 AM, Claudio Freire wrote:
> I have used slony to do database migration. It is a pain to set up,
> but it saves you hours of downtime.
I've had to shoot this option down in two separate upgrade scenarios in
two different companies. Theoretically it's possible, but slony is based
on triggers. If you have an OLTP database with frequent writes, that
overhead (firing the trigger, storing the replicated data, reading the
replication log, traffic to the upgrade node) can literally kill your
application. Downtime is one thing, but maintenance windows can be
planned. Ruining application performance for an undetermined length of
time is probably worse.
Thankfully 8.4 added pg_migrator/pg_upgrade, so that kind of pain is
probably over for the most part. But even without it, 8.4 and above have
parallel restore, which can drop upgrade times down to a fraction of
their former length.
--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 800 | Chicago IL, 60604
312-676-8870
sthomas@peak6.com
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